1. Field of the Invention
The present invention relates to a non-volatile memory element and a manufacturing method thereof. More particularly, the present invention relates to a variable resistance non-volatile memory element which changes its resistance value in response to an electric signal applied thereto.
2. Description of the Related Art
In recent years, with progresses of digital technologies, electronic devices such as portable information devices and information home electric appliances have been developed to provide higher functionalities. With achievement of the higher functionalities of these electronic devices, further miniaturization and higher-speeds of semiconductor elements incorporated into these electronic devices have been progressing at a high pace. Among them, use of a high-capacity non-volatile memory, which is represented by a flash memory, has been expanding at a high pace. Furthermore, as a novel non-volatile memory in a next generation which has a potential of replacing this flash memory, research and development of a variable resistance non-volatile memory device including a variable resistance element has been progressing. The variable resistance element refers to an element having a characteristic in which it reversibly changes its resistance value in response to an electric signal and being able to store information corresponding to the changed resistance value in a non-volatile manner.
International Publication No. 2008/149484 discloses a non-volatile memory element including a first electrode, a second electrode, and a variable resistance layer which is interposed between the first electrode and the second electrode and reversibly changes its resistance value in response to electric signals which are different in polarity from each other and are applied between these electrodes, the variable resistance layer including, in a thickness direction thereof, a first region comprising a first oxygen-deficient tantalum oxide having a composition expressed as TaOx (0<x<2.5), and a second region comprising a second oxygen-deficient tantalum oxide having a composition expressed as TaOy (x<y<2.5).
Japanese Laid-Open Patent Application Publication No. 2010-251352 discloses a non-volatile memory element including a first electrode, a second electrode, and a variable resistance layer which is interposed between the first electrode and the second electrode and reversibly changes its resistance value in response to an electric signal applied between these electrodes, the variable resistance layer having a structure in which a first transition metal oxide layer having a composition expressed as MOx (M is transition metal, and O is oxygen), a second transition metal oxide layer having a composition expressed as MOy (x>y), and a third transition metal oxide layer having a composition expressed as MOz (y>z) are stacked in this order.